The Western Bullldogs have received a major setback as they prepare for their clash with North Melbourne on Saturday afternoon.

In a media statement on Monday, the Bulldogs revealed Robert Murphy will undergo arthroscopic surgery on his right knee to remove a small cyst at the back of his patella tendon. He is expected to miss 2-3 weeks.

Meanwhile, Brad Johnson is expected to miss three weeks after experiencing tightness in his achilles tendon following a training session on Saturday.